1. Field of the Invention
This invention relates to: a wiping unit for a liquid droplet ejection head in a liquid droplet ejection apparatus (imaging apparatus) which uses a liquid droplet ejection head as represented by an ink jet head; a liquid droplet ejection apparatus equipped with the same; an electro-optical device; a method of manufacturing the electro-optical device; and an electronic device.
2. Description of Related Art
An ink jet head (liquid droplet ejection head) of an ink jet printer can accurately eject minute ink droplets (liquid droplets) in a dot shape. Thus, for example, by using a special ink or a function liquid of a photosensitive resin or the like as an ejected liquid, application of the ink jet printer to a manufacturing field of various products is expected.
For example, it has been considered to manufacture a color filter for a liquid crystal display device, an organic EL display device or the like by using a head unit configured by mounting a liquid droplet ejection head, by ejecting liquid droplets toward the workpiece from an ejection nozzle disposed on a downward nozzle surface of the liquid droplet ejection head while moving the head unit relative to a workpiece such as a color filter substrate.
When an apparatus is paused for a relatively long period of time, such as stopping the apparatus, clogging may occur in the ejection nozzle due to increase in viscosity of a function liquid which remains in the liquid droplet ejection head. Thus, a suction unit having a cap to be firmly fixed to the nozzle surface of the liquid droplet ejection head must be arranged in the imaging apparatus, and residual liquid must be sucked from the ejection nozzle for removal by the suction unit during a pause of imaging work. Moreover, since the nozzle surface is contaminated with the sucked-out function liquid when the suction is carried out, it is preferable to wipe off the nozzle surface to remove a stain after the suction.
Thus, there has conventionally been known a wiping unit which comprises a wipe-off unit on which a pressing member for relatively pressing a wiping sheet to a nozzle surface from below is mounted, and a sheet feeding unit to feed the wiping sheet through the pressing member, which is adapted to move the wipe-off unit integrally with the sheet feeding unit in a predetermined wiping direction parallel to the nozzle surface while feeding the wiping sheet in a state in which the wiping sheet is pressed to the nozzle surface, thereby wiping the nozzle surface with the wiping sheet.
In this wiping unit, the wiping sheet is fed substantially horizontally to the pressing member, a cleaning liquid containing a function liquid solvent is ejected from a cleaning liquid nozzle formed in the center of the pressing member to the wiping sheet fed to the pressing member so that the wiping sheet is permeated with the cleaning liquid to effectively wipe off the function liquid stuck to the nozzle surface.
In such a conventional wiping unit, wide planar distribution of a plurality of liquid droplet ejection heads in a carriage causes a problem of interference of the carriage with a main body portion of the wiping unit. Moreover, since the wiping unit is moved by an X-axis table, and the liquid droplet ejection head (carriage) is moved up and down, there is a problem of a complex structure.
In such a case, a structure may be employed in which the wiping unit is disposed on a machine base, the liquid droplet ejection head is arranged to face this unit, and a wiping sheet is introduced from below. Further, if a plurality of liquid droplet ejection heads overlap each other in a wiping direction, or are arranged in a complex manner, a need arises to dispose a supply of a cleaning liquid in one place of a front side in the wiping direction.
However, in such a structure, a surface of the wiping sheet opposing a cleaning liquid ejection member becomes not a front surface (surface brought into contact with the nozzle surface) but a backside, and a cleaning liquid from the cleaning liquid ejection member is applied on this backside. Here, in order to secure absorbency of a removed object by the wiping sheet, a wiping sheet which has a certain thickness must be used, and it takes time for the cleaning liquid applied on the backside of the wiping sheet to permeate the front surface side of the wiping sheet. Thus, in order to widely spread the front surface of the wiping sheet with the cleaning liquid to thereby improve the wiping performance, a distance between the pressing member and the cleaning liquid ejection member must be set long. As a consequence, a consumption amount of the expensive wiping sheet increases to heighten running costs. Namely, in wiping the nozzle surface, it is necessary to start wiping work after the wiping sheet is subjected to preliminary feeding until a portion of the wiping sheet, on which the cleaning liquid is applied by the cleaning liquid ejection member, reaches the pressing member. If the distance between the pressing member and the cleaning liquid ejection member is set large, the length of the wiping sheet wasted by the preliminary feeding becomes large.